Velocity loss with barrel loss

W

Wildcat101

Guest
Hi all,
New member and poster here. I have question regarding velocity loss with shorter barrel lengths. I am working up a load in 257 Roberts to be used in a Ruger Ultra Light with a 20 inch barrel. I am using 115 gr. Nosler Ballistic tip with IMR 4350 powder. I started with 36 gr and increased at 1 gr steps up to 39 grains. 3 shot groups were fired over my Oehler 35P chrono. Results were compared to the expected velocity which are shown in Nosler's manual. Those velocities were clocked in a 24" barrel. My velocities were a little more than 300fps slower at all loadings. I was expecting slower but thought it would be on the order of 120fps based on research done on other sites. I thought maybe I had a chrono problem so I shot another rifle with known velocity and got the expected result. Any thought would be appreciated.

Thanks,
Bob
 
An unschooled opinion

I'm no authority, but remember, you are comparing your factory rifle to Nosler's test rifle. You may have some freebore (depending on the bullet) and a looser chamber and perhaps a looser bore. Also, it's my impression that a smaller hole in the bore means more velocity loss with a loss of barrel length. A 308 might not lose as much as a .257.
 
lots of variables between then and you.
same brass ?
same primer ?
same lot of powder ?
same temp/elevation ?
COAL the same ??
and as was pointed out, the bbls
are different.

what were your velocities ?
( quickload says you are low on pressure at 39 gr)
 
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CMaier said:
lots of variables between then and you.
same brass ?
same primer ?
same lot of powder ?
same temp/elevation ?
COAL the same ??
and as was pointed out, the bbls
are different.

what were your velocities ?
( quickload says you are low on pressure at 39 gr)
Click to expand...

Powder out of the same container, same with primers and brass. Necks turned to 50% clean. Primer pockets uniformed and flash holes de-blurred.
37 gr. 2214 fps. 1.88 group
38 gr. 2279 fps. 1.02 group
39 gr. 2352 fps. 2.45 group. Got impatient with this one and did not let the barrel cool....mistake.

That last group had an ES of 5fps. All powder charges were trickled to .1 gr. Now that I look at my notes the velocities were almost 400fps. under that 24 inch test barrel. Also the bullets were seated .015 off the lands. That seems awfully slow to me. The only thing that I can think of is the powder is about 10 years old. Could it have gone bad? It was stored properly. I am happy with the groups considering how skinny the barrel is but I am not happy about losing so much energy. Plan on using it for deer, 150 yards is a very long shot where I hunt in NY. Not sure what else I can do from a loading perspective. All the groups were fired over a 3 hour period and the weather conditions were pretty constant.
 
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my questions were the "same" as in the nosler book ?

i would keep going up in 1/2 steps and see if you find
another 1" node or less.
watch for pressure signs, but i think you have room
for a bit more powder.
 
Ok, thank you. I really should have understood your question. The only difference I have with the Nosler data is the primer. That is why I started so low looking for pressure, so far none but I will take your advice and bump up the powder as you described. I will post the results when done. This is really a great forum! Thanks again.
 
Keep in mind, the more powder you put in there the more problems you'll have in the long run. It's not like you're going to shoot a group on a deer and if it's not small enough or fast enough the deer wins. In short, load for accuracy rather than speed.....
 
Wilbur said:
Keep in mind, the more powder you put in there the more problems you'll have in the long run. It's not like you're going to shoot a group on a deer and if it's not small enough or fast enough the deer wins. In short, load for accuracy rather than speed.....
Click to expand...

Thanks Wilber,
Maybe I am overthinking this but it seems to me that a quick humane kill is paramount and that is directly related to bullet performance, shot placement, and energy delivered on target. Question is, how much is enough? I have read that 800 ft pounds is minimal for a deer sized animal. My noslers are down to about 1000 ftlbs at 150 yards. While this appears to be adequate I may rethink this combo after some more testing.
 
Screenshot_20161005-213615.jpg
th_BBLlenghtVSvelocity.jpg
[/URL][/IMG] Click image to see on Photobucket.
 
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243winxb said:
What is your data maximum. Different Nosler bullet in this data. Bullet construction does make a difference. . The http://www.hodgdonreloading.com data seems to use a lot more IMR 4350 ?? View attachment 18497
Click to expand...

Wow....the Nosler max load is 40 grains which is below your starting load. I was at the range yesterday with loads creeping up to 40 grains looking for pressure signs. Did not not have any of the signs you would normally look for so I tried 40.5 and no problems there also. Velocity there was 2410 fps.

I know that the Roberts has a commercial +P load and I have conflicting information as to whether this is just a head stamp to identify a factory load to a higher pressure or is the brass structurally different (thicker). If that is the case it is possible that Nosler is listing loads that are compatible only with non +P cases. In other words staying on the safe side. It may also be possible that their loads are lower in case they may be used in old rifles converted to the Roberts.

The brass I am using I bought recently and the do not have +P head stamp so the mystery continues. Thanks. for the very enlightening info!
 
i told you you had room for more powder and still
safe on the pressure side.

any good groups up there ??
 
CMaier said:
i told you you had room for more powder and still
safe on the pressure side.

any good groups up there ??
Click to expand...

40.5 gave me just under 1 inch. Best yet but that is only one group. Don't know if it is repeatable. A lot of weird stuff going on here. Why are Noslers loadigs so low, and why do I have such a velocity drop in my 20" barrel (almost 400 fps) while if you look at that table posted earlier in this thread seems to indicate it should be less than 100 fps. I am going through some other sources to see what their loads are for this bullet weight. I have an old Sierra manual that tops out at about 41.5 or so.
 
modern technology allows better data collection for load books, but then liability and lawyers get involved and who knows
what happens. this is why great software, good notes and common sense can help the ammo crafter get the most
out of reloading.
asking questions is not a bad thing.

Wildcat101 said:
40.5 gave me just under 1 inch. Best yet but that is only one group. Don't know if it is repeatable. A lot of weird stuff going on here. Why are Noslers loadigs so low, and why do I have such a velocity drop in my 20" barrel (almost 400 fps) while if you look at that table posted earlier in this thread seems to indicate it should be less than 100 fps. I am going through some other sources to see what their loads are for this bullet weight. I have an old Sierra manual that tops out at about 41.5 or so.
Click to expand...
 
Wildcat101 said:
This is really good stuff. Where did you get that barrel length data? I can't find it on the Saami web site.
Click to expand...
I got it from Saami and saved it to my photo albums, so i dont have to hunt for it again. http://www.saami.org/specifications_and_information/index.cfm?page=CC The +P is listed as 4000 PSI higher than the standard 257 Roberts. It on SAAMI also. And yes, velocity vs barrel length has been posted on "The High Road" by me and maybe others. http://www.photobucket.com/joe1944usa Link to saved photos i collect.
th_BBLlenghtVSvelocity.jpg
[/URL][/IMG] Click photo link to go there.
 
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Like I said...load for accuracy rather than speed. I don't think you can load an accurate round in a 257 Roberts that won't pass completely through a whitetail's internals. Yes, I know, but I'm somewhat trying to get you to see the light. A slower round that shoots as good as a faster round might be the best in terms of aggravation and case life...you said you're longest (typical) shot is 150 yards. BUT....you ain't me and I respect that. When I was younger, I'd put powder in there until the case broke, and then drop it down to where the case didn't break and shoot the darn thing.
 
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